The research proposal has the general objectives of creating a laboratory animal model of Crohn's disease produced by feeding a sterile, aqueous suspension of bacterial cell wall fragments to rats and of measuring bacterial cell wall antigen and antibody in human patients with Crohn's disease. The intestinal uptake of gavage-fed bacterial cell wall antigen will be measured by immunoassay in rats with normal and nonspecifically inflamed intestines. We will investigate whether gavage-fed bacterial cell wall components can produce chronic granulomatous intestinal inflammation with extraintestinal manifestations in rats, and if this inflammation casn be reactivated by repeat feeding of the cell wall fragments. We will use immunoassays to compare the amount of bacterial cell wall antigen and antibody in the blood and tissue of patients with Crohn's disease with ulcerative colitis patients and controls. Clinical parameters (disease activity and site of disease) will be correlated with assay results. Lymphocytes isolated from the intestinal mucosa and peripheral blood of Crohn's disease patientswill be cultured In Vitro, and the antibody produced measured for activity against bacterial cell wall components.